It would be nice if the link field allowed for advanced type configurations reusing existing types or validators.
Custom labels
A very German example, requiring a fax, not a phone number:
fields:
link:
type: link
options:
- email
- tel
fax:
label: Fax
validate: tel
Custom validators
A custom URL scheme that requires a specific validation rule:
fields:
link:
type: link
options:
- email
- tel
app:
label: App-URL
validate: customvalidator